This invention relates to novel indicator devices for determining the amount of ethylene oxide absorbed during the ethylene oxide sterilization of hospital supplies and related health care materials. The invention is useful in determining when a level of ethylene oxide is reached, upon aeration, which is no longer a health hazard should the sterilization items come into contact with the human body.
Items sterilized with ethylene oxide biocidal gas must be properly aerated so that the release of residual gas during use of the treated item will not cause hemolysis, erythema, and edema of the tissues, or otherwise harm the body. It is estimated that more than 10,000 ethylene oxide sterilization units are installed in U.S. hospitals. Such sterilizers are normally operated at 50.degree.-60.degree. C. and steam is introduced during the biocidal or sterilization cycle to provide the humidity required for the process. This processing results in the breakdown of some of the ethylene oxide to give ethylene glycol and 2-chloroethanol. The latter may be formed during ethylene oxide sterilization when there is a source of chloride as in polyvinyl chloride. Water may react with ethylene oxide to produce ethylene glycol during sterilization.
The Federal Register Vol. 43, No. 122, p. 27482 contains rules (proposed by the Department of Health, Education, and Welfare) that devices contacting blood or large implants shall not contain more than 25 parts per million of ethylene oxide and devices contacting skin shall not contain more than 250 parts per million of ethylene oxide. The laboratory analysis for ethylene oxide is complex, expensive, and time consuming. Therefore, hospitals have relied on aerating for excessively long periods of time to ensure having reached a safe level of residual ethylene oxide biocidal gas. Resulting time delays cause shortages of available materials for hospital operations. excessive stockpiling of hospital items, and often the unknowing use of sterilized items which contain concentrations of ethylene oxide hazardous to health. There exist indicator strips or tags which undergo a permanent color change on exposure to ethylene oxide. These, however, do not show the amount of effective exposure of the items being sterilized. No simple indicators are available which attest to the adequacy of the items being sterilized. No simple indicators are available which attest to the adequacy of ethylene oxide exposure or which give the residual ethylene oxide remaining after exposure. The Canadian Government has recognized an urgent need for the type of device described in this invention and has granted approximately 250 thousand dollars to support the development of the product of this invention.